π-0 transition in superconductor-ferromagnet-superconductor junctions

Superconductor-ferromagnet-superconductor (SFS) Josephson junctions are known to exhibit a transition between π and 0 states. In this letter, we find the π-0 phase diagram of an SFS junction depending on the transparency of an intermediate insulating layer (I). We show that, in general, the Josephson critical current is nonzero at the π-0 transition temperature. Contributions to the current from the two spin channels nearly compensate each other, and the first harmonic of the Josephson current as a function of phase difference is suppressed. However, higher harmonics give a nonzero contribution to the supercurrent.     

Variable electrostatic transformer: controllable coupling of two charge qubits

We propose and investigate a novel method for the controlled coupling of two Josephson charge qubits by means of a variable electrostatic transformer. The value of the coupling capacitance is given by the discretized curvature of the lowest energy band of a Josephson junction, which can be positive, negative, or zero. We calculate the charging diagram of the two-qubit system that reflects the transition from positive to negative through vanishing coupling. We also discuss how to implement a phase gate making use of the controllable coupling.     

Determination of serotonin and bufotenin as their dansyl derivatives.

A method is described which permits the determination of serotonin and bufotenin in the same tissue sample. It comprises the following steps: (a) tissue extraction with acetone-0.1 M hydrochloric acid (19:1); (b) reaction of the tissue extract with dansyl (Dns) chloride; (c) pre-separation of O-Dns-bufotenin from O,N-bis-Dns-serotonin and other Dns-amides on a small silica gel column (this step is dispensable if only serotonin or bufotonin is being determined); (d) TLC separation of O-Dns-bufotenin and O,N-bis-Dns-serotonin from other Dns derivatives; (e) quantitative evaluation of the separated compounds by fluorimetry for O-Dns-bufotenin and by fluorimetry or mass spectrometry for the serotonin derivative. The photometer response is linear within the range 0.1-300 nmole. With the mass spectrometric method, 2 pmole of O,N-bis-Dns-serotonin could be determined with a standard deivation of +/-9%. The recovery of the amines from tissue was better than 85%. Reserpine treatment of toads caused a concomitant decrease in serotonin and bufotenin in the brain, but not in the skin of the animals. Repletion of bufotenin in the brain occurs at a higher rate than the repletion of the serotonin pool.